Full resolution (JPEG) - On this page / på denna sida - Second part - IX. Mining Industry and Metal Production - 1. The Iron Mines (together with information regarding other mines). By the late Prof. O. G. Nordenström - Technics of mining
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technics of mining.
703
The catting of the coal in the pillars is done by means of stalls which are
driven parallel with the main stalls and with the same width as these. These
stopes are afterwards entirely filled.
Ventilation and lighting. According to observations made in a large
number of Swedish ore-mines, it is known that the temperature in them rises
one degree centigrade for every 50 meters under the level (30 meters below the
snrface) at which the temperature is constant the year round, or the same as
the mean temperature of the air above ground in that vicinity. In the deepest
mines, the temperature rises up to 11 or 13 degrees Celsius, and in those of
medium depth, 6 to 8 degrees. Since the average temperature at the surface in
onr mining districts varies between 3-7, 5, and 6 degrees, the natural ventilation
caused hereby is sufficient to give due ventilation to most of the ore-mines in
this country. Artificial ventilation is used only exceptionally, and is produced partly
by centrifugal ventilators and partly by Harz-mine ventilators (HarzerWettersatz).
In coal-mines the air is exchanged to a large extent by means of natural
ventilation, or on account of great difference between the temperature of the air
on the surface and down in the mine.
The ventilation hereby brought about is not alone sufficient, however, to cause
the necessary exchange of air, and is therefore supported by placing furnaces or,
more usually, only an open fire at the bottom of the shaft, from which the bad
air is to be expelled, or the air is warmed up by means of steam-injectors, or
simply by steam-pipes. — The use of furnaces or open fires for ventilation is not
accompanied by any danger, since fire-damp has never been observed to exist in
the coal-mines of Sweden. Thus the costs of ventilation are almost none in the
ore-mines, and in the coal-mines very slight.
For the lighting of the working-chambers down in the mines, open lamps
are used both in ore-mines and coal-mines. As a rule, benzoline (gasoline),
petroleum, or more seldom rape-oil, are burned in these lamps. Tallow candles are
also. used in some mines. In the mines which have electric hoisting-works, electric
light is used, both on the surface and down in the mines.
Hoisting and pumping. The deepest iron mines have a vertical depth of
hardly more than 350 meters, and as to other mines, only a few of them are more
than 400 meters deep. In most of the mines the depth is less than 100 meters,
or varies between 100 and 200 meters. The amount of röck and water which
has to be hoisted out of each shaft is, furthermore, as a rule, very small, and
consequently the hoisting and pumping machinery generally does not require
engines of many horse-power. The power generally varies from 20 or 30 to, at
the most, 80 or 90 horse-power. At the largest ore-fields, however, still more
powerful hoisting engines and pumps are used.
The shafts are generality perpendicular, some of them are rectangular
and some circular. The area of the horizontal section of old shafts runs up
to about 40 sq. m. The modern shafts are, as a rule, rectangular, and their
greatest section-area is 18 to 20 sq. m. The influx of water is, as has
already been implied, very small. As a rule, it amounts, at the most, to 200,
300, or 500 liters per minute. For removing the water from the smaller
mines, suction and lift pumps are used; in the larger mines,- plunger pumps, the
pressure-height of the latter being generally 150 meters, once in a while 200 to
220 meters.
The transportation of the coal down in the coal-mines, if long, is executed
by means of horses of small breed or by traction machinery. The hoisting and
pumping machinery is much stronger in the coal-mines than in the ore-mines.
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